The objectives of this research have been to characterize swine plasma lipoproteins, develop radioimmunoassays to measure a major apoprotein of swine VLDL, LDL and HDL for use in studying lipoprotein metabolism in the isolated perfused pig liver. The lipoproteins have been characterized and the radioimmunoassays have been developed and a perfusion system developed. Studies to be carried out will include the evaluation of the effect of insulin, glucagon, glucose, and free fatty acids on the synthesis and release of lipoproteins. Concommitantly, we will evaluate the effect of these substances on HMG CoA reductase activity and fatty acid synthetase activity. We will also evaluate the role of the liver in LDL catabolism by following the disappearance of 125I-LDL and the appearance of non trichloroacetic acid precipitable non iodide labeled material in the perfusate.